Electrocardiographic (ECG) Q- and ST-T–wave abnormalities predict coronary heart disease (CHD) and total mortality. No comparison has been made of the classification of these abnormalities by the 2 most widely used ECG coding systems for epidemiologic studies—the Minnesota Code (MC) and Novacode (NC). We evaluated 12-lead electrocardiograms from 64,597 participants (49 to 79 years old, 82% non-Hispanic white) in the Women’s Health Initiative clinical trial in 1993 to 1998, with a maximum of 11 years of follow-up. We used MC and NC criteria to identify Q-wave, ST-segment, and T-wave abnormalities for comparison. In total, 3,322 participants (5.1%) died during an average 8-year follow-up, and 1,314 had incident CHD in the baseline cardiovascular disease-free group. Independently, ECG myocardial infarction criteria by the MC or NC were generally equivalent and were strong predictors for CHD death and total mortality (hazard ratio 1.62, 95% confidence interval 1.05 to 2.51 for CHD death; hazard ratio 1.36, 95% confidence interval 1.09 to 1.71 for total mortality) in a multivariable analytic model. Electrocardiograms with major ST-T abnormalities by the MC or NC coding system were stronger in predicting CHD deaths and total mortality than was the presence of Q waves alone. In conclusion, the ECG classification systems for myocardial infarction/ischemia abnormalities from the MC and NC are valuable and useful in clinical trials and epidemiologic studies. ST-T abnormalities are stronger predictors for CHD events and total mortality than isolated Q-wave abnormalities.
Among the coding systems for classification of electrocardiographic (ECG) abnormalities, the Minnesota Code (MC), introduced in the early 1960s, is the most widely used in epidemiologic studies and clinical trials. The MC was designed for morphologic categorization of ECG waveform features and was an important step forward in standardization of measurement and classification of morphologic ECG features. The Novacode (NC) system is an extension of the MC and is a hierarchic coding scheme that was developed initially in the late 1980s and further refined in 1998 and is still evolving. The 2 coding systems have been used in many recent epidemiologic studies and clinical trials. However, no comparison has been made of code-specific myocardial infarction (MI)/ischemia classification by these 2 coding systems. The present study compared and evaluated the value of the current MC and NC for prevalent MI/ischemia for the prediction of incident fatal and nonfatal coronary heart disease (CHD) and total mortality.
Methods
The Women’s Health Initiative (WHI) clinical trial is a multicenter study of risk factors for the prevention of common causes of mortality, morbidity, and impaired quality of life in US postmenopausal women. Detailed eligibility criteria and recruitment methods, randomization, follow-up, data and safety monitoring, and quality assurance have been published previously. The study was approved by each study site’s institutional review board. All participants provided written informed consent.
Of the 68,133 WHI clinical trial participants who were enrolled from 1993 to 1998, 974 without complete ECG data, 1,839 with QRS duration ≥120 ms (an external pacemaker, Wolff-Parkinson-White pattern, or major ventricular conduction defects), and 723 with inadequate quality electrocardiograms were excluded from analysis. The remaining 64,597 participants at baseline were stratified into 2 groups: those with cardiovascular disease (n = 11,284) to test the predictive power of prevalent ECG criteria for CHD death and total mortality and those without cardiovascular disease (n = 53,313) to test the predictive power of ischemia (no MI) ECG criteria for incident CHD. The cardiovascular disease group was identified by the presence of ECG MI evidence or a history of angina, coronary artery bypass surgery, coronary angioplasty, or congestive heart failure and was included in the total cohort to test the predictive value of combined prevalent MI/ischemia criteria for the duration of the trial.
Average follow-up was 8 years (maximum 11 years). Three outcomes were considered in the present investigation: (1) incident CHD events (fatal and nonfatal) only for the cohort free of cardiovascular disease at baseline, (2) CHD death, and (3) all-cause mortality. After baseline, deaths and hospitalization events were ascertained by annual follow-up calls, review of vital records, and community surveillance of hospitalized and fatal events. Incident CHD events for women free of cardiovascular disease at baseline included clinical MI, evolving Q-wave ECG MI, coronary death, hospitalized angina pectoris, and coronary revascularization. Clinical MI was categorized using an algorithm that included symptoms, ECG findings, and cardiac enzyme measurements. Detailed definitions for the diagnosis of acute MI and death due to CHD were previously published and are based on standardized criteria.
Identical electrocardiographs (MAC PC, Marquette Electronics, Inc., Milwaukee, Wisconsin) were used at all clinic sites, and simultaneous 12-lead electrocardiograms at rest were recorded in all participants using strictly standardized procedures. Chest electrodes were located in precise positions. All electrocardiograms were processed in a central ECG laboratory (Epidemiological Cardiology Research Center [EPICARE], Wake Forest University, Winston-Salem, North Carolina), where they were visually inspected for technical errors and inadequate quality. Processing of electrocardiograms was repeated for the present study with the 2001 version of the GE Marquette 12-SL program (Marquette 12SL ECG Physician Guide, available at http://www.ge-healthcare.com ). The Marquette measurement matrix contained several ECG measurements of MI/ischemia that were used as outcome variables in this study.
NC designates 1 code as NC 5 with 9 hierarchies for MI/ischemia, i.e., NC-5.1 for major Q waves, NC-5.2 for moderate Q waves with major ST-T abnormalities, NC-5.3 for moderate Q waves without major ST-T abnormalities, NC-5.4 for minor Q waves with major ST-T abnormalities, NC-5.5 for isolated major ST abnormalities, NC-5.6 for isolated major T-wave abnormalities, NC-5.7 for minor Q waves, and NC-5.8 for minor ST-T abnormalities. NC MI was identified by NC-5.1 to NC-5.4 ( Online Appendix 1 , Table 1 ) and NC ECG ischemia was identified as NC-5.5 to NC-5.8.
| Category | Novacode | Minnesota Code ⁎ | ||
|---|---|---|---|---|
| Major Q waves | NC-5.1 | Q score ≥35 | MC-C.1 | MC 1-1-X |
| Moderate Q waves with ST-T abnormalities | NC-5.2 | Q score ≥25 and ST-T score ≥20 | MC-C.2 | MC 1-2-X plus MC 4-1, 4-2, MC 5-1, 5-2 |
| Moderate Q waves without ST-T abnormalities | NC-5.3 | Q score ≥25 and ST-T score <20 | MC-C.3 | MC 1-2-X |
| Minor Q waves with ST-T abnormalities | NC-5.4 | Q score ≥15 and ST-T score ≥20 | MC-C.4 | MC 1-3-X plus MC 4-1, 4-2, MC 5-1, 5-2 |
| Isolated/major ST abnormalities | NC-5.5 | ST-segment depression score ≥20 and Q score <15 and no left ventricular hypertrophy by Cornell voltage | MC-C.5 | MC 4-1, 4-2 |
| Isolated/major T-wave abnormalities | NC-5.6 | T-wave negativity score ≥20 and Q score <15 and no left ventricular hypertrophy by Cornell voltage | MC-C.6 | MC 5-1, 5-2 |
| Minor Q waves | NC-5.7 | Q score ≥15 and ST-T score <20 | MC-C.7 | MC 1-3-X |
| Minor ST-T abnormalities | NC-5.8 | ST-T score ≥10 | MC-C.8 | MC 4-3, 4-4, or MC 5-3, 5-4 |
| No significant Q waves or ST-T change | NC-5.0 | Q score <15 and ST-T scores <10 | MC-C.0 | MC 1-0 and MC 4-0 and MC 5-0 |
| Electrocardiographic myocardial infarction by Novcode or Minnesota Code | NC-MI | NC-5.1 to NC-5.4 | MC-MI | MC-C.1 to MC-C.4 |
⁎ C is the code standard for the combined code of codes 1, 4, and 5 of the Minnesota Code to match the hierarchical codes in Novacode 5.
MC MI/ischemia criteria incorporates 4 MC codes and each with 3 subcodes to define and locate 3 selective sites—anterolateral, posterior (inferior), or anterior—and uses the following 4 codes at each site: code 1 for Q and QS patterns, code 4 for ST-segment depression, code 5 for T-wave negativity, and code 92 for ST-segment elevation. Among these codes, MI/ischemia MC is categorized as MC 1-1-X for major Q waves, MC 1-2-X for moderate Q waves, MC 1-3-X for minor Q waves, MC 4-1 or 4-2 for major ST depression, MC 5-1 or 5-2 for major T abnormality, and MC 4-3 or 4-4 or MC 5-3 or 5-4 for minor ST-T abnormality. To achieve equivalency with the NC 5, 9 hierarchic combined codes (MC-C) of MC 1, MC 4, and MC 5 were categorized in the following way for illustration in the accompanying tables ( Online Appendix 2 , Table 1 ): category MC-C.1 for major Q wave, MC-C.2 for moderate Q wave with major ST-T change, MC-C.3 for moderate Q wave without major ST-T change, MC-C.4 for minor Q wave with major ST-T change, MC-C.5 for major ST depression, MC-C.6 for major T wave change, MC-C.7 for minor Q wave, and MC-C.8 for minor ST-T change. Then the MC for MI was identified by categories MC-C.1 to MC-C.4 to match the NC for MI (NC-5.1 to NC-5.4). MC ECG ischemia was identified as MC-C.5 to MC-C.8.
The total cohort of 64,597 and the 53,313 without cardiovascular disease at baseline were analyzed separately for 3 end points. Frequency distributions of all ECG and non-ECG variables were first inspected to rule out anomalies and outliers possibly due to measurement artifacts. Descriptive statistics were used to determine means, SDs, and percentiles for continuous variables and frequencies and percentages for categorical variables.
Cox proportional hazards regression was used to assess effects of ECG variables on risk of CHD events and total mortality and to test and compare baseline (prevalent) MI/ischemia codes by MC or NC as predictors of each of the 3 studying end points. To minimize confounding, covariates associated with risk of incident CHD event and total mortality were included for analysis. All risk models were adjusted for age only and then for key demographic and clinical characteristics, which are listed in the Tables 2 and 3 . All analyses were performed using SAS 9.1.3 (SAS Institute, Cary, North Carolina).
| Characteristics | Total | CVD Free | CVD | p Value |
|---|---|---|---|---|
| (n = 64,597) | (n = 53,313) | (n = 11,284) | (CVD free vs CVD) | |
| Age (years), mean ± SD | 63 ± 7 | 62 ± 7 | 65 ± 7 | <0.001 |
| Body mass index (kg/m 2 ), mean ± SD | 29 ± 6 | 29 ± 6 | 30 ± 6 | <0.001 |
| Blood pressure (mm Hg), mean ± SD | ||||
| Systolic blood pressure | 128 ± 17 | 127 ± 17 | 130 ± 18 | <0.001 |
| Diastolic blood pressure | 76 ± 9 | 76 ± 9 | 76 ± 9 | <0.001 |
| Non-Hispanic white | 52,658 (81.5%) | 43,538 (81.7%) | 9,120 (80.8%) | <0.05 |
| African-American | 6,583 (10.2%) | 5,224 (9.8%) | 1,359 (12.0%) | <0.05 |
| Education (≤ high school) | 15,358 (23.9%) | 12,472 (23.6%) | 2,886 (25.8%) | <0.001 |
| Presently married/living as married | 40,332 (62.7%) | 33,729 (63.6%) | 6,603 (58.8%) | <0.001 |
| Current smoking | 5,093 (8.0%) | 4,194 (8.0%) | 899 (8.1%) | <0.01 |
| Hypertension | 21,709 (33.9%) | 16,219 (30.7%) | 5,490 (49.1%) | <0.001 |
| Diabetes mellitus | 4,001 (6.2%) | 2,831 (5.3%) | 1,170 (10.4%) | <0.001 |
| Hypercholesterolemia ⁎ | 7,328 (12.7%) | 5,208 (11.0%) | 2,120 (20.4%) | <0.001 |
| Asthma | 4,932 (7.7%) | 3,787 (7.2%) | 1,145 (10.3%) | <0.001 |
| Emphysema/chronic bronchitis | 2,025 (3.5%) | 1,469 (3.1%) | 556 (5.3%) | <0.001 |
| Cancer | 2,615 (4.1%) | 2,062 (3.9%) | 553 (5.0%) | <0.001 |
| Kidney stone | 2,312 (4.0%) | 1,743 (3.7%) | 569 (5.5%) | <0.001 |
| Previous stroke | 702 (1.1%) | 416 (0.8%) | 286 (2.5%) | <0.001 |
| Cardiovascular disease (cardiovascular disease history † , electrocardiographic myocardial infarction ‡ ) | 11,284 (17.5%) | (0%) | (100%) | <0.001 |
| Family history of coronary heart disease | 10,855 (18.7%) | 8,347 (17.4%) | 2,508 (24.8%) | <0.001 |
| Total mortality | 3,322 (5.1%) | 2,382 (4.5%) | 940 (8.3%) | <0.001 |
| Coronary heart disease death | 538 (0.8%) | 317 (0.6%) | 221 (2.0%) | <0.001 |
| Incident coronary heart disease § | 1,314 (2.5%) | |||
| Electrocardiographic characteristics | ||||
| Electrocardiographic myocardial infarction (by Minnesota Code or Novacode) ‡ | 1,818 (2.8%) | 0 | 1,818 (16.1%) | <0.001 |
| Myocardial infarction by Novacode | 923 (1.4%) | 0 | 923 (8.2%) | <0.001 |
| Myocardial infarction by Minnesota Code | 1,655 (2.6%) | 0 | 1,655 (14.8%) | <0.001 |
| Novacode for myocardial infarction/ischemia ‡ | ||||
| NC-5.1 | 92 (0.1%) | 0 | 92 (0.8%) | <0.001 |
| NC-5.2 | 71 (0.1%) | 0 | 71 (0.6%) | <0.001 |
| NC-5.3 | 460 (0.7%) | 0 | 460 (4.1%) | <0.001 |
| NC-5.4 | 300 (0.5%) | 0 | 300 (2.7%) | <0.001 |
| NC-5.5 | 1,356 (2.1%) | 844 (1.6%) | 512 (4.5%) | <0.001 |
| NC-5.6 | 1,080 (1.7%) | 716 (1.3%) | 364 (3.2%) | <0.001 |
| NC-5.7 | 3,756 (5.8%) | 2,388 (4.5%) | 1,368 (12.1%) | <0.001 |
| NC-5.8 | 11,673 (18.1%) | 9,463 (17.8%) | 2,210 (19.6%) | <0.001 |
| NC-5.0 | 45,809 (70.9%) | 39,902 (74.8%) | 5,907 (52.4%) | <0.001 |
| Combinations of Minnesota Code for myocardial infarction/ischemia ‡ | ||||
| MC-C.1 | 484 (0.8%) | 0 | 484 (4.3%) | <0.001 |
| MC-C.2 | 112 (0.2%) | 0 | 112 (1.0%) | <0.001 |
| MC-C.3 | 794 (1.2%) | 0 | 794 (7.0%) | <0.001 |
| MC-C.4 | 265 (0.4%) | 0 | 265 (2.4%) | <0.001 |
| MC-C.5 | 902 (1.4%) | 532 (1.0%) | 370 (3.3%) | <0.001 |
| MC-C.6 | 1,632 (2.5%) | 1,147 (2.2%) | 485 (4.3%) | <0.001 |
| MC-C.7 | 3,145 (4.9%) | 2,553 (4.8%) | 592 (5.3%) | <0.001 |
| MC-C.8 | 6,912 (10.7%) | 5,498 (10.3%) | 1,414 (12.5%) | <0.001 |
| MC-C.0 | 50,351 (78.0%) | 43,583 (81.8%) | 6,768 (60.0%) | <0.001 |
⁎ Hypercholesterolemia identified by self-reported pill use for cholesterol.
† Cardiovascular disease history indicates the presence of electrocardiographic myocardial infarction evidence, history of clinical myocardial infarction, angina, coronary artery bypass surgery, coronary angioplasty, or congestive heart failure at the time the participant entered the study baseline.
‡ See Table 1 for electrocardiographic myocardial infarction criteria.
§ Incident coronary heart disease includes myocardial infarction, coronary death, hospitalized angina pectoris, and coronary revascularization.
| No. (event rates) ⁎ | HR † (95% CI) | HR ‡ (95% CI) | |
|---|---|---|---|
| Electrocardiographic myocardial infarction by Minnesota Code/Novacode § | |||
| NC-MI | 35 (3.8%) | 3.73 (2.64–5.26) | 1.62 (1.05–2.51) |
| MC-MI | 55 (3.3%) | 3.52 (2.66–4.65) | 1.56 (1.08–2.26) |
| Novacode 5 § | |||
| NC-5.1 | 6 (6.5%) | 10.1 (4.48–22.7) | 3.42 (1.24–9.44) |
| NC-5.2 | 3 (4.2%) | 5.31 (1.70–16.6) | 2.82 (0.88–9.02) |
| NC-5.3 | 6 (1.3%) | 1.97 (0.87–4.42) | 0.68 (0.22–2.17) |
| NC-5.4 | 20 (6.7%) | 8.63 (5.46–13.7) | 3.74 (2.10–6.66) |
| NC-5.5 | 47 (3.5%) | 4.73 (3.45–6.48) | 3.05 (2.10–4.45) |
| NC-5.6 | 24 (2.2%) | 3.54 (2.32–5.38) | 1.68 (0.99–2.84) |
| NC-5.7 | 60 (1.6%) | 2.41 (1.81–3.20) | 1.71 (1.22–2.41) |
| NC-5.8 | 128 (1.1%) | 1.78 (1.43–2.20) | 1.52 (1.18–1.96) |
| NC-5.0 | 244 (0.5%) | ||
| Combinations of Minnesota Code for myocardial infarction/ischemia § | |||
| MC-C.1 | 16 (3.3%) | 4.90 (2.96–8.12) | 2.11 (1.15–3.89) |
| MC-C.2 | 3 (2.7%) | 3.57 (1.14–11.1) | 1.71 (0.42–7.02) |
| MC-C.3 | 18 (2.3%) | 3.21 (2.00–5.18) | 1.64 (0.90–3.02) |
| MC-C.4 | 18 (6.8%) | 8.34 (5.17–13.5) | 3.08 (1.63–5.81) |
| MC-C.5 | 35 (3.9%) | 4.93 (3.46–7.01) | 3.11 (2.06–4.70) |
| MC-C.6 | 32 (2.0%) | 3.10 (2.15–4.47) | 1.94 (1.26–3.00) |
| MC-C.7 | 35 (1.1%) | 1.65 (1.16–2.35) | 1.41 (0.93–2.13) |
| MC-C.8 | 94 (1.4%) | 2.05 (1.62–2.59) | 1.65 (1.25–2.16) |
| MC-C.0 | 287 (0.6%) | ||
| Adjusted variables † | |||
| Black versus white | 1.96 (1.54–2.49) | ||
| High school versus college degree | 2.21 (1.25–3.91) | ||
| Divorced/separated versus currently married | 2.01 (1.60–2.52) | ||
| Current smoking versus Never smoked | 3.68 (2.87–4.71) | ||
| Hypertension (yes vs no) | 2.67 (2.24–3.19) | ||
| Diabetes mellitus (yes vs no) | 5.04 (4.15–6.12) | ||
| Hypercholesterolemia (yes vs no) | 2.32 (1.90–2.84) | ||
| Asthma (yes vs no) | 1.33 (0.99–1.79) | ||
| Emphysema/chronic bronchitis (yes vs no) | 2.16 (1.54–3.02) | ||
| Cancer (yes vs no) | 1.67 (1.20–2.32) | ||
| Kidney stone (yes vs no) | 1.28 (0.85–1.94) | ||
| Previous stroke (yes vs no) | 3.82 (2.62–5.56) | ||
| Cardiovascular disease (cardiovascular disease history, electrocardiographic myocardial infarction) (yes vs no) | 2.73 (2.29–3.24) | ||
| Family history of coronary heart disease (yes vs no) | 1.70 (1.39–2.09) | ||
| Body mass index (per SD) | 1.33 (1.23–1.43) | ||
| Systolic blood pressure (per 10 mm Hg) | 1.18 (1.13–1.23) | ||
| Diastolic blood pressure (per 10 mm Hg) | 1.08 (0.99–1.18) | ||
| Hematocrit (per 10%) | 1.47 (1.22–1.76) | ||
| White blood cell count (kcell/ml) (per 10 kcell) | 1.03 (0.99–1.07) |
⁎ Event rates of electrocardiographic myocardial infarction or each MC-C and NC-5 code.
‡ Additionally adjusted by key demographic and clinical variables: ethnicity, body mass index, education, marriage status, smoking status, alcohol use, asthma, emphysema, cancer, diabetes mellitus, hypertension, kidney stones, hypercholesterolemia, previous stroke, history of cardiovascular disease, systolic blood pressure, diastolic blood pressure, hematocrit, white blood cell, total calories, dietary cholesterol, family history of coronary heart disease, and study component/arm groups (hormone therapy/dietary modification/calcium and vitamin D).
§ See Table 1 .
Results
Of 64,597 participants, 82% were non-Hispanic white and 10% were African-American. Average age of the study group at baseline was 63 ± 7 years and 34% had hypertension, 6.2% had diabetes, and 18% had a history of cardiovascular disease or presence of verified ECG MI by the MC or NC. There were 2.8% ECG MIs by the NC or MC, 22% with any ECG Q-wave ST-T change by MC-C.1 to C.8 and 29% with any change by NC-5.1 to 5.8. A total of 3,322 (5.1%) participants died during an average 8 year follow-up in the total study cohort, and 1,314 in the cardiovascular disease–free group had incident CHD during a maximum of 11-year follow-up ( Table 2 ). Prevalent MI was greater for the MC (2.6%) than for the NC (1.4%).
Tables 3 and 4 present age and multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of the ECG MI/ischemia codes for CHD death ( Table 3 ) and total mortality ( Table 4 ) for all study participants. As presented in Table 3 , ECG MI by the MC or NC was a strong predictor for CHD death in women. There was a 50% increased risk for CHD death by the MC or NC in the multivariable model with adjusted demographic and clinical variables. Furthermore, for each hierarchical code, there was an increased risk of CHD mortality. Electrocardiograms with Q wave plus major ST-T abnormality indicated significantly increased risk for CHD death for MC-C.4 (HR 3.08, 95% CI 1.63 to 5.81) and the equivalent NC-5.4 (HR 3.74, 95% CI 2.10 to 6.66), whereas electrocardiograms with minor ST-T abnormalities or minor Q-wave changes alone also had an order of magnitude lower but increased risk for CHD death for MC-C.8 (minor ST-T abnormality, HR 1.65, 95% CI 1.25 to 2.16) and for the equivalent NC-5.7 (minor Q-wave changes, HR 1.71, 95% CI 1.22 to 2.41).
| No. (event rates) ⁎ | HR † (95% CI) | HR ‡ (95% CI) | |
|---|---|---|---|
| Electrocardiographic myocardial infarction by Minnesota Code/Novacode § | |||
| NC-MI | 118 (12.8%) | 2.09 (1.74–2.51) | 1.36 (1.09–1.71) |
| MC-MI | 188 (11.4%) | 1.94 (1.68–2.25) | 1.27 (1.05–1.53) |
| Novacode 5 § | |||
| NC-5.1 | 17 (18.5%) | 3.80 (2.36–6.13) | 2.48 (1.48–4.16) |
| NC-5.2 | 12 (16.9%) | 2.79 (1.58–4.93) | 1.85 (0.99–3.48) |
| NC-5.3 | 41 (8.9%) | 1.73 (1.27–2.36) | 1.11 (0.75–1.62) |
| NC-5.4 | 48 (16.0%) | 2.76 (2.07–3.68) | 1.68 (1.19–2.39) |
| NC-5.5 | 178 (13.1%) | 2.33 (2.00–2.72) | 1.83 (1.53–2.20) |
| NC-5.6 | 88 (8.2%) | 1.67 (1.35–2.07) | 1.21 (0.94–1.55) |
| NC-5.7 | 265 (7.1%) | 1.36 (1.20–1.55) | 1.13 (0.97–1.31) |
| NC-5.8 | 713 (6.1%) | 1.26 (1.15–1.37) | 1.16 (1.05–1.29) |
| NC-5.0 | 1,960 (4.3%) | ||
| Combinations of Minnesota Code for myocardial infarction/ischemia § | |||
| MC-C.1 | 61 (12.6%) | 2.60 (2.02–3.36) | 1.63 (1.21–2.20) |
| MC-C.2 | 18 (16.1%) | 3.04 (1.91–4.84) | 1.96 (1.15–3.35) |
| MC-C.3 | 68 (8.6%) | 1.67 (1.32–2.13) | 1.16 (0.87–1.56) |
| MC-C.4 | 41 (15.5%) | 2.72 (1.99–3.70) | 1.45 (0.98–2.14) |
| MC-C.5 | 125 (13.9%) | 2.45 (2.04–2.94) | 1.83 (1.48–2.26) |
| MC-C.6 | 121 (7.4%) | 1.60 (1.33–1.93) | 1.24 (1.00–1.53) |
| MC-C.7 | 197 (6.3%) | 1.27 (1.10–1.47) | 1.05 (0.89–1.25) |
| MC-C.8 | 532 (7.7%) | 1.59 (1.45–1.75) | 1.32 (1.18–1.48) |
| MC-C.0 | 2,159 (4.3%) | ||
| Adjusted variables § | |||
| Black versus white | 1.35 (1.21–1.50) | ||
| High school versus college degree | 1.75 (1.38–2.21) | ||
| Divorced/separated versus currently married | 1.58 (1.44–1.73) | ||
| Current smoking versus never smoked | 3.52 (3.17–3.90) | ||
| Hypertension (yes vs no) | 1.54 (1.44–1.65) | ||
| Diabetes mellitus (yes vs no) | 2.44 (2.22–2.69) | ||
| Hypercholesterolemia (yes vs no) | 1.30 (1.18–1.43) | ||
| Asthma (yes vs no) | 1.35 (1.20–1.52) | ||
| Emphysema/chronic bronchitis (yes vs no) | 2.37 (2.08–2.70) | ||
| Cancer (yes vs no) | 1.40 (1.21–1.62) | ||
| Kidney stone (yes vs no) | 1.10 (0.92–1.32) | ||
| Previous stroke (yes vs no) | 2.07 (1.69–2.54) | ||
| Cardiovascular disease (cardiovascular disease history, electrocardiographic myocardial infarction) (yes vs no) | 1.60 (1.48–1.72) | ||
| Family history of coronary heart disease (yes vs no) | 1.30 (1.19–1.42) | ||
| Body mass index (per SD) | 1.14 (1.10–1.18) | ||
| Systolic blood pressure (per 10 mm Hg) | 1.10 (1.08–1.12) | ||
| Diastolic blood pressure (per 10 mm Hg) | 1.07 (1.03–1.11) | ||
| Hematocrit (per 10%) | 1.22 (1.11–1.34) | ||
| White blood cell count (Kcell/ml) (per 10 kcell) | 1.03 (1.01–1.04) |
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